Wandering are there any areas in the continental US that have zero light pollution meaning the night skies are as they were 1000 years ago or is everywhere affected by man made light pollution even if it is to a micro degree?

Wandering are there any areas in the continental US that have zero light pollution meaning the night skies are as they were 1000 years ago or is everywhere affected by man made light pollution even if it is to a micro degree?

Do you mean the continental US or the contiguous US? Continental includes Alaska, which averages much less light pollution than the Lower 48.

Regardless, almost by definition, nowhere has zero light pollution. As the saying goes, nature abhors a vacuum. You can come close to zero but never reach it.

Are there areas where light pollution is undetectable by the most sensitive instruments available? Almost certainly not in the Lower 48, if you include only areas with unobstructed views in every direction. Almost certainly yes, if you include areas where part of the view is blocked up to 20 degrees above the horizon. Essentially all the light from a truly distant city will be below that.

For instance, the lights of Moab are surely detectable from the plateau in Canyonlands National Park, but almost certainly not from an even modestly deep canyon there.

There are large areas of the Lower 48 where artificial skyglow is small or negligible compared to natural skyglow. And since natural skyglow varies considerably from one night to the next, your question about 1,000 years ago is oddly phrased. In those areas, the sky tonight might be brighter than it was 1,000 years ago but darker than it was 1,000 years and one day ago.

I concur with Tony, there is simply no location in the lower 48 that is absolutely pristine with regard to absolute darkness as would have been encountered here a millennium ago. Since traces of strong man-made light pollution are detectible at some minute level for hundreds of miles surrounding the source in an otherwise totally dark region, subtle effects of it will always be present.

I concur with Tony, there is simply no location in the lower 48 that is absolutely pristine with regard to absolute darkness as would have been encountered here a millennium ago.

However, as also noted in my post, there are many areas where artificial light pollution has no effect on the stargazing experience.

It's a little hard for Easterners to grasp this. There's a truly huge amount of de facto wilderness in the West. Almost all of the western U.S. is much darker than areas that are considered not bad in the East, like Stellafane. Perhaps 80% of the West is darker than areas that are considered excellent in the East, like Cherry Springs. And the darkest 20% to 30% of the West (an area bigger than the entire Eastern Seaboard) is mighty close to pristine.

I was in the Tanzania a few ago on the plains and I was expecting black skies but it really wasn't much different than Cherry Spring, which is a great place though over the past 5 years I have noticed a change for the worse. The Western states have less moisture in the air also which has to help as far as 'seeing' and 'transparency'. Would like to travel out there with the scope some day.

Yes, and I have been to one just recently- the US Forest Service's Cosmic Campground, being built by Alma, New Mexico. It has skies where the Milky Way looks like a solid object in the sky. The dust lanes are like they were cut out with an Xacto knife.

It just got its clear sky clock, which is centered on the GPS coordinates I took in the center of the observing area:

The roads are in place, but it is still under construction. This is the first time the Forest Service has done this, so it is a bit of an experiment. The site will ultimately have toilet facilities and have 10' square concrete telescope pads. We came up with a drawing to put acid etched orientation lines from the surveyor on the slabs so you will be able to plop down a scope in daylight and be north aligned by putting two legs on an east west line, or using one of the north south lines as a reference.

They really have gone all out for this- you will be able to reserve it for like $50/ night and camp there with your RV and have it all to yourself or for your group.

Alma is quite small, but does have a general store with all basic necessities up through RV deep cycle batteries, so unlike hitting the west Texas area or central Nevada, it's pretty civilized. If it is successful, the hope is the US Forest Service, which owns territory in basically all dark zones in the US, will use this as a model for more of these.

Go offshore. It's technically still U.S. property and there's ZERO light pollution especially when you darken the ship. It's amazing how bright the natural starlight gets.

You have to go quite a bit further than our territorial waters, which are only 12 miles. Sailing down the eastern seaboard on a clear night, you can still see substantial sky glow over metropolitan areas as far out as 50 miles or more.

Folks love to banter back and forth over the internet claiming this or that site is surely the definition of pristine and clearly of Bortle Class 1. Some even claim to supposedly have seen these conditions surpassed!

However, I would point to the lead sentence from the origin published description defining some particular features of that class of sky conditions that never seems to be cited by the observer touting their location:

"The zodiacal light, gegenschein, and zodiacal band are all visible — the zodiacal light to a striking degree, and THE ZODIACAL BAND SPANNING THE ENTIRE SKY."

When you actually see conditions such as this it truly leaves the observer in awe of the night sky's true appearance. I've encountered such a couple of times in the distant past and talked with some other very experienced observers from far flung corners of the earth who have seen it too...but not any in many years now and certainly none in the U.S.A.

According to the new light pollution atlas (when I plot more contours below the current lowest black/dark gray contour), the darkest area in the lower 48 US (at zenith) is southeast Oregon and northwest Nevada. The center of this dark region is in Oregon maybe about halfway between Sheldon National Antelope Refuge and Steens Mountain. The next darkest area in the lower 48 is Big Bend National Park, particularly the southeast part. There is a region in the northern half of Baja California, however, that is "darker" than either of these places.

In the end though, this isn't really important. As mentioned above, when the sky is dark, variations in natural sky brightness dominate and moreover issues like the typical transparency and seeing of a site become the most important issues when selecting a site to observe.

Way back about a decade when I was still working somebody provided me with a GIS map showing areas of the United States with no sky glow visible.

The area you mentioned in Oregon was one of the few areas in the entire US with no sky glow visible.

From the Forest Service point of view I was looking for "pristine" skies and how they related to Wilderness areas. Unfortunately, in the lower 48 it is now really difficult to find any areas without visible sky glow.

That is a real sad fact when you think about it. An entire country with very, very few areas where light from man's activities are not visible.

The Okanogan-Wenatchee National Forest located an observing pad at Meadows Campground. Probably the darkest remaining site in Washington state. The road up to the campground is a real adventure and you hit some pretty spectacular country just wandering north on the PCT to Canada.

There is another thread on the site about Escalante, UT - I've observed from south of that town and not been able to see an artificial light or detect a light dome. Ditto for Natural Bridges, also in Utah.

I have no idea if the light domes of smallish towns scores of miles away are detectable with sensors but the sky looked like the description given by Brooks above on a good night.

The zodiacal light, gegenschein, and zodiacal band are all visible — the zodiacal light to a striking degree, and THE ZODIACAL BAND SPANNING THE ENTIRE SKY.

When you actually see conditions such as this it truly leaves the observer in awe of the night sky's true appearance. I've encountered such a couple of times in the distant past and talked with some other very experienced observers from far flung corners of the earth who have seen it too...but not any in many years now and certainly none in the U.S.A.

I haven't seen this myself, but I have seen many such accounts from recent years in the U.S. and southern Canada.

Although low levels of light pollution are certainly a prerequisite for such observations, they're by no means sufficient. It also requires excellent transparency -- and observing at the right time of year. The Gegenschein is not visible when it's near the Milky Way.

Incidentally, my first sighting of the Gegenschein was from a site with significant light domes in a couple of directions.

Go to the Okie-Tex Star Party and be prepared for an amazing sight. It is so dark there Venus casts shadows, and you will be able to see very clearly by starlight alone. It is the only place were I only needed a Telrad to find every single object I could think to look for with my 10-inch with ease.

According to the new light pollution atlas (when I plot more contours below the current lowest black/dark gray contour), the darkest area in the lower 48 US (at zenith) is southeast Oregon and northwest Nevada. The center of this dark region is in Oregon maybe about halfway between Sheldon National Antelope Refuge and Steens Mountain. The next darkest area in the lower 48 is Big Bend National Park, particularly the southeast part.

I have made two trips to Big Bend National Park in late winter (very reasonable temps in February and March), and the night sky there is truly something else. There's dark, really dark, and then there's (bleep)ing dark, and Big Bend is in the last category. Any place where you can see Barnard's Loop with the naked-eye is a keeper. The Horsehead Nebula was visible on three straight nights with a set of *unfiltered* 25x100 binoculars. My eyes are pretty good, but not Stephen-O'Meara-good. I could see down to mag-7.7 w/o optical aid at Big Bend. My previous best was 7.4-mag at Spruce Knob and 7.3 at both Cherry Springs and Calhoun County Park, WV.

Which brings up a good point--there are places in the Eastern U.S. that gives you a taste of Desert-SW darkness overhead, BUT...get anywhere away from the cozy confines of the zenith, and that's where the Desert SW really starts to pull away. Dark is one thing, but dark and dry with superb transparency *literally* opens up the entire sky up for serious observing. From Big Bend, I could see M13 with the naked-eye before the entire Keystone had risen above the eastern horizon. Not only could we see the Eta Carinae Nebula a little more than 1 degree above the horizon, we could also make out extensive nebulosity in a 12" dob. Even that low above the horizon, you could tell that object was intricate and HUGE.

I guess while the differences in zenith brightness at the darkest areas in the light pollution atlas may be undetectable at zenith, they are a good proxy for the darkness of the sky in other directions. So for the least interference from light domes in the lower 48, you should go to SE Oregon/NW Nevada or Big Bend.

My home isn't 30 miles from Manhattan, yet I can recall instances in recent years when humidity and particulate levels were so low, and the resulting transparency levels so high, that the LM at the zenith reached 6th magnitude for an hour or two; mag 5.2 is a typical "good" evening here.